1. Field of the Invention
This invention relates to a new process for preparing polyol-catalyst mixtures. More particularly, the invention relates to a new process for preparing polyol-catalyst mixtures which are useful in the preparation of improved rigid polyurethane cellular products.
Specifically, the invention provides a new process for simultaneously preparing a polyol-catalyst mixture which can be used to produce improved rigid polyurethane cellular products, which process comprises reacting a Mannich base compound, water and an epoxide, such as ethylene oxide, together at an elevated temperature, and subsequently removing the water from the reaction mixture. The invention further provides new and valuable polyurethanes, and particularly new rigid polyurethane cellular products having a high content of isocyanurate linkages, improved heat distortion temperatures and improved insulating properties, which products are prepared by reacting the aforementioned polyol-catalyst mixture with a polyisocyanate.
2. Description of the Prior Art
It is known to prepare rigid polyurethane foams by the reaction of a polyisocyanate with a hydroxyl-terminated polyester, polyether or polyamine, which generally have hydroxyl numbers within the range of from about 350 to 900. However, to date no ideal polyol has been found and, for various reasons, polyurethane foams prepared from such polyols have not been entirely satisfactory.
Still further, the production of a satisfactory urethane foam requires that the relative rates of the various reactions that occur be properly balanced. This balance is normally obtained by careful selection of a catalyst system. The catalyst usually consists of a tertiary amine used alone or, when necessary, mixed with organic tin compounds in a manner well known to those skilled in the art. The tertiary amines so employed will normally impart an objectionable odor to the final foam product.
U.S. Pat. No. 3,297,597 proposes the use of certain nitrogen-containing polyols which act both as a polyol and a catalyst in the reaction with the polyisocyanates. This avoids some of the difficulties noted above, such as the odor of the amine catalyst, but still retains some of the limitations of the prior known products, such as limited heat resistance, limited compatibility and limited isocyanurate linkages retained in the cured product.
It is an object of the invention, therefore, to provide a new process for preparing polyol-catalyst mixtures useful in the preparation of polyurethane foams. It is a further object to provide a process for preparing new polyol-catalyst mixtures which impart many improvements to the preparation of rigid polyurethane cellular products. It is a further object to provide new polyol-catalyst mixtures for polyurethane foam preparation which permit the production of products having a higher number of isocyanurate linkages. It is a further object to provide new polyol-catalyst mixtures for polyurethane production which permits slower and more desirable reaction. It is a further object to provide new polyol-catalyst mixtures which give polyurethane foamed products having improved heat resistance and insulation properties. It is a further object to provide new polyol-catalyst mixtures which have better compatibility with the reaction components. It is a further object to provide new polyol-catalyst mixtures which are simple and economical to prepare. These and other objects of the invention will be apparent from the following detailed description thereof.